The present invention relates to a machine for making filter tipped cigarettes, cigars or cigarillos, and more particularly to an apparatus for monitoring filter rod sections in filter tipping machines. Still more particularly, the invention relates to an apparatus for monitoring filter rod sections (especially filter plugs of double unit length) in filter tipping machines of the type wherein filter tipped smokers' products are produced by placing a rod-shaped filter component of double unit length between a pair of coaxial rod-shaped tobacco-containing components of unit length and by draping an adhesive-coated uniting band around the filter component and the adjacent ends of the tobacco-containing components of unit length. Each filter component of double unit length may contain a filler of one and the same filter material, a composite filler which consists of two or more different filter materials, or each filter component may constitute a so-called recessed filter plug. For the sake of simplicity, the invention will be described with reference to machines for the making of filter tipped cigarettes with the understanding, however, that the improved apparatus can be resorted to with equal advantage in the manufacture of filter tipped cigars or cigarillos.
A modern filter tipping machine turns out large numbers of filter cigarettes per unit of time. Therefore, it is important to insure that the machine can operate without interruptions for extended intervals of time because each and every interruption, even a very short one, entails production losses amounting to thousands of filter cigarettes. Such machines are equipped with means for transporting pairs of coaxial spaced-apart plain cigarettes of unit length along a first path and for feeding filter plugs of double unit length along a second path toward and into the gaps between coaxial plain cigarettes of successive pairs. Furthermore, such machines are equipped with devices for forming adhesive-coated uniting bands which are draped around successive filter plugs and the adjacent ends of coaxial plain cigarettes to form tubes which connect the filter plugs with the respective plain cigarettes. The resulting filter cigarettes of double unit length are thereupon severed so that each thereof yields two filter cigarettes of unit length which are tested and some of which are tip-turned so that all filter mouthpieces face in the same direction. The resulting row of filter cigarettes of unit length is thereupon transported to the next processing station, e.g., directly into the magazine of a packing machine. The timing of delivery of pairs of plain cigarettes and filter plugs of double unit length is such that, as a rule, the thus obtained groups of three coaxial rod-shaped articles each form a continuous row moving at a high speed through a draping station, a severing station, one or more testing stations, a tip turning station and toward the outlet of the machine. Provision is made to eliminate all causes of potential malfunction, such as the absence of adhesive-coated uniting bands, the absence of one or more plain cigarettes, improper orientation of rod-shaped components during transport through the filter tipping machine and/or others. Continuing interruptions of the delivery of plain cigarettes, filter plugs and/or uniting bands normally entail immediate stoppage of the machine in order to reduce the number of rejects. However, it happens from time to time that temporary absence of certain components (e.g., filter plugs) is less damaging than even short-lasting stoppage of the filter tipping machine, especially if such machine forms part of a complete production line which further includes one or more cigarette makers, a packing machine, a carton filling machine and/or others. In such situations, it is more economical to maintain the machine in operation for a given interval of time and to accept a certain number of rejects (which are segregated upon testing of the final products) than to arrest the machine and thereby cause losses in output which, within a few minutes, can run into tens of thousands of filter cigarettes. A typical example of the just outlined situation is temporary absence of filter plugs of double unit length. A certain number of filter plugs is likely to fail to reach the assembly station where the filter plugs are inserted between pairs of coaxial plain cigarettes of unit length for a number of reasons, such as temporary failure of the mechanism which transports filter plugs to the assembly station, clogging of one or more flutes in the conveyors which transport filter rod sections of e.g., six times unit length toward and past severing devices which subdivide each relatively long section into filter plugs of double unit length, improper operation of means for retaining the filter plugs in their path during transport toward the assembly station and/or certain other factors.
If a filter plug of double unit length fails to reach the assembly station and the corresponding pair of coaxial plain cigarettes of unit length continues to advance toward the draping station, the uniting band which is applied to such plain cigarettes is likely to become separated therefrom because, as a rule, the band contacts only the innermost portions of wrappers of the plain cigarettes. In the absence of a filter plug in the interior of the convoluted uniting band, the latter is not sufficiently stiff to withstand deforming stresses during further transport of corresponding plain cigarettes through the filter tipping machine. A detached uniting band is likely to adversely affect the operation of the machine, not only because it becomes stuck at a particular point but especially because its adhesive coat contaminates the machine so that the contaminated part or parts interfere with orderly transport of satisfactory groups of coaxial rod-shaped articles through the machine. Sooner or later, one or more improperly applied uniting bands will cause a serious malfunction which is detected, either automatically or by the attendant, and whose elimination necessitates a lengthy interruption of operation of the filter tipping machine or the entire production line.